Dependence of the velocity dispersion on the SFR and the rotational velocity. In the left panel, we show the model by Krumholz et al. (2018) with the feedback as the only driver of the velocity dispersion. In the central panel, we show the model with the release of gravitational energy due to the transport of the gas across the disk as the only driver of the velocity dispersion. In the right panel, we show the model with the combination of feedback and transport as drivers of the velocity dispersion.